Modifications are made to the global model developed by Fremouw, et al. for the incremental electron density of F-layer irregularities in order to force the model into agreement with a considerable body of scintillation and spread-F data. While special attention is given to the equatorial region, where the original model was particularly lacking, the results of other studies are used to update the model in the other latitude regions and so provide a model of general application. The model now embodies the effect of magnetic activity at all latitudes, variations of occurrence with longitude in the equatorial region, variability of the width and position of the equatorial region, the influence of irregularity layer thickness, irregularity shape and electron density power spectrum, as well as the diurnal, seasonal and sunspot cycle variations of irregularity occurrence and strength at all latitudes. The improvements proposed not only enhance the model's usefulness as a simulation technique in engineering applications, but should also provide an impetus to the understanding of the physics of the irregularities.